No Blue Light has the perfect tones to keep your screen blue light free. Unlike blue light glasses, this utility protects not just your eyes but your skin from the harmful effects of blue light. The app should be on everyone's mac as its free, doesn't slow your mac down, sips little battery and will stay free as part of my perfect eyesight project. The app includes a keyboard shortcut to easily toggle between modes and the option to switch between up to 3 modes, Off, Medium, and Full intensity protection. Personally I keep it on all day with atleast 40% intensity and 100% at night time for a good circadian rythem.